Ovarian estradiol (E) stimulates cellular proliferation in the human endometrium; during the secretory phase luteal progesterone (P) inhibits further E-induced proliferation of the luminal epithelium. The rodent has been used extensively as a model of hormonal control of uterine growth. In the ovariectomized (ovxd) rodent E stimulates DNA synthesis in uterine, cervical, and vaginal epithelia; P blocks E stimulation of uterine and cervical epithelia but not vaginal epithelium. Glucocorticoids also block the effect of E on uterine growth in rodents. In animals pretreated with P, E stimulates mitotic activity of the uterine stroma (subepithelial). High-dose progestin therapy is used to treat endometrial hyperplasia and endometrial carcinoma. It has been assumed that the mode of action in this therapy is to inhibit E-driven cellular events. However, recent evidence in rodents indicates that P inhibits uterine epithelial DNA synthesis that is ongoing in the absence of estrogen. In two models of estrogen-independent uterine epithelial growth, progestins and glucocorticoids inhibit DNA synthesis. The goal of the present proposal is to investigate the mechanisms of: 1) progestin and glucocorticoid inhibition of uterine epithelial proliferation; 2) E stimulation of uterine stromal DNA synthesis in P treated animals; 3) E stimulation of uterine and vaginal epithelial proliferation. Since both progestins and glucocorticoids inhibit uterine epithelium of rodents, two questions arise: 1) Do glucocorticoids inhibit human uterine epithelial proliferation? 2) Is P or glucocorticoid inhibition of the uterus mediated by the progesterone receptor (PR) or the glucocorticoid receptor? The first question will be answered by examining the response of human tissue to glucocorticoids in xenograft (athymic mouse). The second question will be answered by performing a number of studies comparing the modes of action of the two classes of steroids in the E-stimulated, and the E-independent models of uterine epithelial DNA synthesis in rodents. Proposed studies will: 1) examine the "E-independent" models for signs of activated estrogenic mechanisms, i.e. the state of the estrogen receptor (cytosolic vs. nuclear fraction) and PR content; 2) determine the cell cycle specificities of the progestin and glucocorticoid responses; 3) compare relative binding affinities and dose response curves for several steroids with differing degrees of glucocorticoid and progestin activity; and 4) compare the effects of 3 antiprogestins with differing degrees of antigulcocorticoid activity. Possible interactions of the epithelia and stroma in determining the proliferative activity under hormonal influence will also be examined. Epithelial ablation in situ will determine whether that tissue is a necessary component of the stromal response to E in P-treated uterus. Heterotypic epithelial and stromal tissue recombinants will define the tissue source of the signal produced by hormones (E or E + P) administered. Expression of cellular homologs of viral oncogenes (c-onc) during E-stimulation and P-inhibition will be examined. Techniques of tissue separation to be used offer a defined system in which to examine the possible correlation of c-onc with hormonal stimulation.